1. Field of the Invention
The present invention is an additive preparation for use in collection devices wherein the additive preparation effervesces when in contact with a body fluid. The additive preparation desirably comprises a formulation comprising an additive such as a clot activator, anticoagulant or urine preservation material, an organic acid and a metal carbonate compound. The effervescence effect of the formulation aids in dispersal and delivery of the additive in a body fluid sample. The formulation is desirably tableted to provide an effective, easily stored and handled preparation. In particular, the formulation of the present invention preferably comprises a clot activator or anticoagulant, an organic acid and a metal carbonate compound wherein the formulation enhances clot activation or the anticoagulant effect in a blood specimen.
2. Description of Related Art
Blood collected in evacuated tubes often must be clotted prior to clinical examination because it is desirable to form a dense clot as rapidly and completely as possible to facilitate clean separation of the clot from the serum layer by centrifugation. To achieve this end, both plastic and glass blood collection tubes frequently employ a clot activator. Typical clot activators are diatomaceous earth and particles of inorganic silicates, or biochemicals such as ellagic acid, thrombin, trypsin and thromboplastin.
Typical clot activators used commercially are silica coated on fabric, silica particles in small plastic cups or silicate particles applied to the tube wall with a polyvinylpyrrolidone (PVP) carrier. However, in these type of arrangements, it is necessary for the user to initiate mixing of the sample so that the activator is bioavailabile to the specimen thus providing the desired effect of the additive in the sample. Therefore, the mixing requirement is critical to obtaining the desired effect of the additives.
Maximum effectiveness is achieved by thorough dispersion of the clot activator throughout the blood sample. Since clot activator materials are generally in powder form or as a wall coating, mixing of the clot activator with the blood sample to achieve dispersion may be a physically awkward operation. Also complete dispersion of the clot activator material in the blood sample tends to be frustrated by the tendency of the clot activator material to agglomerate upon moistening.
In addition, agglomerated clot activator particles tend to settle relatively rapidly, according to Stokes Law, which provides that the settling rate of a particle in a dispensing fluid will be governed by its relative diameter and density as well as the fluid's viscosity and density.
Therefore, there is a need for providing a means for deploying an additive in a body fluid with minimal requirements of the user to initiate mixing of the additive and the body fluid and whereby the additive is able to provide rapid and reliable performance under variable handling conditions.
More particularly, there is a need for a blood collection tube with means for promoting clot-acceleration of a blood sample which provides an enhanced rate of blood coagulation (shortened time for blood coagulation) without leaving any substantial amount of soluble or particulate material in the serum layer on centrifugation, thus avoiding potential interference with clinical tests, particularly in blood banking procedures. Whereas there are numerous commercial products available that employ clot activators, these products are unable to satisfactorily provide a shortened time for blood coagulation or provide a sample with minimal soluble or particulate material in the serum layer.